Two-dimensional transition metal carbide/nitrides, typically represented by Ti3C2Tx, have been believed as a potential novel microwave absorption material because of their unique two-dimensional (2D) laminated structure, native defects and abundant surface chemistry. However, its intrinsic single dielectric loss mechanism limits the future improvement of microwave absorption properties. Herein, we report a simple solvothermal route for in situ heterogeneous nucleation and growth of Fe3O4 magnetic nanoparticles on the Ti3C2Tx MXene surface and interlayer, which is denoted as Fe3O4@Ti3C2Tx nanocomposites, thus balancing the impedance matching, introducing more loss mechanism and enhancing microwave absorption performance. Interestingly, the solvothermal process provides a reducing environment which protects Ti3C2Tx MXene from oxidation at temperature up to 200 degrees C, endowing Ti3C2Tx MXene a high stability compared with hydrothermal process. The sample containing 25 wt% Fe3O4 exhibits an impressive microwave absorption performance, the minimum RL of -57.2 dB at 15.7 GHz and an effective absorption bandwidth of 1.4 GHz (thickness 4.2 mm), which is mainly attributed to the suitable impedance matching, enhanced interface polarization and Debye relaxation caused by unique laminated heterointerface structure of Fe3O4@Ti3C2Tx. This work provides a simple and novel strategy for the modification of MXene and the development of high performance MXene based microwave absorbing materials.